The present invention relates to a reel lock mechanism for a tape cassette in which a pair of tape reels accommodated within a cassette housing can be prevented from being rotated by engagement between ratchet wheels formed on outer peripheral portions of the tape reels and a ratchet when the tape cassette is not in use and a method of assembling the reel lock mechanism.
Tape cassettes for use with video recording and/or reproducing apparatus, such as a video cassette recorder (VCR) and an 8-mm video cassette recorder (8-mm VCR), including a reel lock mechanism for preventing rotation of a pair of tape reels having a magnetic tape wound thereon when they are not in use.
A reel lock mechanism is generally composed of a reel lock body, a pair of reel lock ratchets, a ratchet opening spring and a slide spring. The reel lock body can be moved close to or away from a pair of supply and take-up reels under the spring force of the slide spring. The reel lock body has at its right and left portions the pair of reel lock ratchets pivotally supported thereon. The pair of reel lock ratchets are opened outward under the spring force of the ratchet opening spring and ratchet portions formed at the tip ends of the reel lock ratchets are meshed with the ratchets formed on the outer peripheral portions of the pair of reels.
In the above-mentioned tape cassette, the ratchet opening spring for the pair of reel lock ratchets has two coil portions. Therefore, when the reel lock mechanism having such shaped ratchet opening spring is assembled, the following two assembly methods have been proposed.
The first assembly method encounters the following problem. Because the ratchet opening spring has two coil portions, initially, only one coil portion is attached to a shaft portion of one reel lock ratchet by twisting an arm of the coil portion. Then, under the condition that the arm of the coil portion which has been attached to the shaft portion of one reel lock ratchet can be prevented from being disengaged from the shaft portion, the other coil portion is attached to a shaft portion of the other reel lock ratchet by twisting an arm of the other coil portion. During assembly, those who assemble the tape cassettes have to do two kinds of operations at the same time. Therefore, if those who assemble the tape cassettes are not skillful, the ratchet opening spring will not be attached to the shaft portion of the reel lock ratchet. Therefore, the assembly of the tape cassette needs a skillful worker.
The second assembly method encounters the following problem. Initially, the two coil portions of the ratchet opening spring are installed on the shaft portions of the right and left reel lock ratchets. Then, the right and left arms are respectively engaged with spring engagement ribs under twisting force. If a tape cassette is small, then assemblies thereof also are small and hence the arms of the ratchet opening spring are not long enough to be readily picked up when the arms are engaged with the spring engagement ribs. As a result, the ease of effecting the assembly is not satisfactory.